The primary objectives of this study are to assess in young adult survivors (age >18) of childhood brain tumors the impact of contemporary treatment (surgery, RT, chemotherapy or a combination). The integrity of the hypothalamic-pituitary-gonadal axis, semen quality in men, and ovulatory function in females will be assessed. The 24 hour leuprolide stimulation test will be utilized to assess the HPG axis in all study subjects. A single semen sample will be obtained from all male subjects to determine sperm quantity and quality. Basal body temperatures, day 3 plasma FSH, midcycle urinary LH and midluteal plasma progesterone levels will be employed to assess ovulatory status and potential for fertility in menstruating females.